First up, to get the EVGA 4WAY Mobo working with 5 GPUs I had to go into bios and set "low memory gap" to "3G" instead of "Auto"...dont ask me why, but it worked :)

Next I had to roll back my drivers to 190.62

Finally in order to get BOINC to see the gpus they had to be active in nvidia control panel... enabling sli on my 295s allowed boinc to see 4 gpus, enabling physx on my 285 allowed boinc to see the 5th